Based on LS-1691, this document defines specifications for HB3 LED light sources. LED light sources shall not exceed the specified envelope, function in either voltage polarity, and be rotated in the measuring holder until the reference lug contacts the holder plane. Essential electrical and photometric characteristics include rated values at 12V and 13.2V, with minimum luminous flux of 2000 lm and cap temperature limits. Luminous flux measured at elevated ambient air temperature shall be at least 75% of objective luminous flux. Screen projection requirements specify box system proportions for light emitting areas and contrast limits. Normalized luminous intensity distribution shall comply with specified limits in defined C-planes when measured at test voltage.